1. Field of the Invention
The present invention relates generally to automated hard copy apparatus, such as ink-jet printers, and more specifically to an adjustable carriage mount for aligning an automated writing instrument, such as an ink-jet printhead, with respect to a printing zone of the apparatus.
2. Description of Related Art
The art of ink-jet technology is relatively well developed. Commercial products such as computer printers, graphics plotters, copiers, and facsimile machines employ ink-jet technology for producing hard copy. The basics of this technology are disclosed, for example, in various articles in the Hewlett-Packard Journal, Vol. 36, No. 5 (May 1985), Vol. 39, No. 4 (August 1988), Vol. 39, No. 5(October 1988), Vol. 43, No. 4 (August 1992), Vol. 43, No. 6 (December 1992) and Vol. 45, No. 1 (February 1994) editions. Ink-jet devices are also described by W. J. Lloyd and H. T. Taub in Output Hardcopy [sic] Devices, chapter 13 (Ed. R. C. Durbeck and S. Sherr, Academic Press, San Diego, 1988).
FIG. 1 (PRIOR ART) depicts an ink-jet hard copy apparatus, in this exemplary embodiment a computer peripheral printer, 101. A housing 103 encloses the electrical and mechanical operating mechanisms of the printer 101. Operation is administrated by an electronic controller 102 (usually a microprocessor or application specific integrated circuit (xe2x80x9cASICxe2x80x9d) controlled printed circuit board) connected by appropriate cabling to a computer (not shown). It is well known to program and execute imaging, printing, print media handling, control functions and logic with firmware or software instructions for conventional or general purpose microprocessors or with ASIC""s. Cut-sheet print media 105, loaded by the end-user onto an input tray 120, is fed by a suitable paper-path transport mechanism (not shown) to an internal printing zone 107 where graphical images or alphanumeric text is created. A carriage 109, mounted on a carriage rod, or slider, 111, scans the print zone 107. An encoder subsystem 113, 201 is provided for keeping track of the position of the carriage 109 at any given time. A set of individual ink-jet pens, or print cartridges, 115x are releasably mounted in the carriage 109 and fluidically coupled, such as by flexible tubing 119, to ink reservoirs 117x (generally, in a full color system, inks for the subtractive primary colors, cyan, yellow, magenta (CYM) and true black (K) are provided; an ink fixer chemical (F) is also sometimes provided). Once a print job is completed, the print medium is ejected onto an output tray 121. The carriage scanning axis is conventionally designated the x-axis, the print media transit axis is designated the y-axis, and the printhead firing direction is designated the z-axis. [For convenience of describing the ink-jet technology and the present invention, all types of print media are referred to simply as xe2x80x9cpaper,xe2x80x9d all compositions of colorants are referred to simply as xe2x80x9cink,xe2x80x9d and all types of hard copy apparatus are referred to simply as a xe2x80x9cprinter.xe2x80x9d No limitation on the scope of invention is intended nor should any be implied.]
In essence, the ink-jet printing process involves digitized dot-matrix manipulation of drops of ink ejected from a pen onto an adjacent paper. One or more ink-jet type writing instruments (also referred to in the art as an xe2x80x9cink-jet penxe2x80x9d or xe2x80x9cprint cartridgexe2x80x9d) includes a printhead which generally consists of drop generator mechanisms and a number of y-axis aligned columns of ink drop firing nozzles of a substantially planar nozzle plate superjacent the drop generator mechanisms. Each column or selected subset of nozzles (referred to in the art as a xe2x80x9cprimitivexe2x80x9d) selectively fires ink droplets (typically each being only a few picoliters in liquid volume) that are used to create a predetermined print matrix of dots on the adjacently positioned paper as the pen is scanned across the media. A given nozzle of the printhead is used to address a given matrix column print position on the paper (referred to as a picture element, or xe2x80x9cpixelxe2x80x9d). Horizontal positions, matrix pixel rows, on the paper are addressed by repeatedly firing a given nozzle at matrix row print positions as the pen is scanned. Thus, a single sweep scan of the pen across the paper can print a swath of tens of thousands of dots. The paper is stepped to permit a series of contiguous swaths. Complex digital dot matrix manipulation is used to form alphanumeric characters, graphical images, and photographic reproductions from the ink drops. Page-wide ink-jet printheads are also contemplated and are adaptable to the present invention. Thus, it can be recognized that a critical operating factor is printhead-to-paper spacing and alignment to ensure accurate dot placement.
FIG. 2 (Prior Art) schematically illustrates a typical pen-to-paper alignment scheme. The front of the carriage 109 (with respect to the leading edge of a sheet of paper 105 in the print zone 107 supported by a platen or suspended by a paper pivot apparatus (neither shown)) is used as a pivot point xe2x80x9cAxe2x80x9d and known manner camming mechanisms (not shown) are provided on at least one end of the slider 111. Note that mechanical tolerances inherent in such rod adjustment mechanisms can be the source of vibration of the rod and hence the carriage and pens. Letting xe2x80x9cTheta-Xxe2x80x9d represent the pitch angle of the printhead 201 with respect to a Y-plane, it can be recognized that Theta-X is not held when adjusting the slider up or down (as represented by the arrows Z-up and Z-down) with the carriage 109 pivoting about point xe2x80x9cA.xe2x80x9d Therefore, another adjustment mechanism would be required to ensure pitch axis parallelism between the printhead 201 and the paper 105. It can also now be recognized that other degrees of freedom of the printhead 201 must be accounted for; let xe2x80x9cTheta-Yxe2x80x9d represent the roll angle of the printhead with respect to an X-plane, and let xe2x80x9cTheta-Zxe2x80x9d represent the yaw angle of the printhead nozzle columns with respect to the Y-axis. When both Theta-Z=0xc2x0 and Theta-X=0xc2x0, the long axisxe2x80x94that is, the columns of nozzlesxe2x80x94of the printhead 201 is parallel to the paper transport Y-axis; when Theta-Y=0xc2x0, the short axis of the printheadxe2x80x94that is, a line perpendicular to the columns of nozzlesxe2x80x94is parallel to the carriage scanning X-axis.
There is a need for an adjustable carriage mount which will provide independent carriage alignment.
In its basic aspects, the present invention provides a system for aligning a writing instrument to a print medium, including: a support base having a substantially fixed position; a chassis for retaining the writing instrument; and a plurality of support mechanisms for coupling the chassis to the base, each of the support mechanisms having alignment mechanisms for independently adjusting spacing between the chassis and the base wherein pitch angle and roll angle of the writing instrument with respect to the print medium is determined by adjusting each of the support mechanisms.
In another basic aspect, the present invention provides an ink-jet hard copy apparatus, including: a base having a substantially fixed spatial orientation; a print zone having a substantially fixed spatial orientation with respect to the base; a chassis for retaining at least one ink-jet printhead device in a predetermined orientation the print zone; and a plurality of supports for coupling the chassis to the base, each of the supports being fixedly mounted to the base and each of the supports having a range of settable distance positions wherein setting the distance between the printhead device and the print zone simultaneously adjusts the printhead device pitch and roll angle with respect to the print zone.
In another basic aspect, the present invention provides a method for adjusting the spatial orientation of an ink-jet printhead to a printing zone of an ink-jet hard copy apparatus. The method includes the steps of: providing at least three independently adjustable printhead mounts for setting the distance between the printhead and the printing zone; and independently adjusting the printhead mounts to set the pitch angle and roll angle of the printhead to predetermined settings.
The method and apparatus can be automated by providing known manner sensing mechanisms for detecting real-time orientation of the printhead to the printing zone and providing signals indicative of the orientation, and automatically adjusting the printhead mounts based on the signals such that a predetermined orientation of the printhead is maintained with respect to the printing zone.
Some of the advantage of the present invention are:
it solves problems attendant to the prior art;
it provides a simple mechanism for adjusting pen-to-paper alignment whereby a printhead can be aligned to be parallel to adjacently positioned print media;
it provides for pen-to-paper height and both Theta-X and Theta-Y adjustment;
it frees the carriage rod in a scanning ink-jet device from mechanisms for adjusting pen-to-paper height, wherein the carriage rod can have better mechanical tolerances and integrity;
it substantially eliminates print quality problems induced by an adjustable, vibrating carriage rod; and
it is adaptable to a fully automated implementation.
The foregoing summary and list of advantages is not intended by the inventor to be an inclusive list of all the aspects, objects, advantages and features of the present invention nor should any limitation on the scope of the invention be implied therefrom. This Summary is provided in accordance with the mandate of 37 C.F.R. 1.73 and M.P.E.P. 608.01(d) merely to apprise the public, and more especially those interested in the particular art to which the invention relates, of the nature of the invention in order to be of assistance in aiding ready understanding of the patent in future searches. Other objects, features and advantages of the present invention will become apparent upon consideration of the following explanation and the accompanying drawings, in which like reference designations represent like features throughout the drawings.